In 1967, using sodium aluminate, silica gel, tetraethyl ammonium hydroxide (TEAOH) and water, Wadlinger of Mobile Corp first synthesized a zeolite beta through mixing-crystallization. The zeolite beta is characterized by a high silica-alumina ratio, which can vary in a wide range. Martens et, al. proclaimed that, by using decane as a probe, the zeolite beta had a porous framework structure of 12-member ring; in 1988, Newsam and Higgins et. al. determined for the first time that the zeolite beta had a stacking fault structure by framing model and simulating powder diffractometry. The zeolite beta has a 12 member-ring structure with intersected porous channels, wherein the pore diameter of the 12-member ring is 075-0.57 nm for one-dimension porous channel parallel to the (001) crystal face, while the pore diameter of the 12 member-ring is 0.65-0.56 nm for the two-dimension porous channel parallel to the (100) crystal face. The zeolite beta is a high silica zeolite with macropores and a three-dimension structure that is only one discovered up to now, and has both acid catalytic property and structural selectivity due to its structural particularity, and further has very high thermostability (the failure temperature of the crystal lattice is higher than 1200° C.), hydrothermal stability and wear-resistant property. Due to the unique structural feature, the zeolite beta has good thermal and hydrothermal stability, acid resistance, anti-coking property and catalytic activity in a series of catalytic reactions, showing excellent performance in aspects of catalysis, adsorption and the like, therefore it has broad prospects in applications and has been developed rapidly into a new-type of catalytic materials in recent years. After modified or supported with some metal components, the zeolite beta can be used for petroleum refining and petrochemical processes such as hydrocracking, hydroisomerization, hydration of olefins, and the like.
In many catalytic chemical reaction processes, there is need to use the zeolite supported or exchanged with metals or metal ions (such as Ni, Co, Cu, Ag, Zn, Fe, Mn, Cr, Zr, Mo, W, alkali earth metal, rare earth metal and the like) as an active component of catalyst.
CN 1098028A discloses a zeolite beta catalyst for reactions of toluene disproportion and transalkylation, the catalyst consists of 10-90 wt % of zeolite beta, 5-90 wt % of a binder and 0.05-5 wt % of metals selected from the group consisting of Ni, Co, Cu, Ag, Sn, Ga and the like, wherein the metals are supported by means of immersion.
U.S. Pat. No. 5,453,553 discloses a process for preparing dodecylbenzene through the reaction of benzene and laurylene, wherein the catalyst used is obtained by supporting one or more transition metals selected from Fe, Ni, Co, Pt and Ir on a zeolite selected from X-, Y-, M-, ZSM-12 or zeolite betas. These metals are supported in pores of the zeolite by impregnating, the catalysts can obviously improve the stability of the catalyst used in synthesis of dodecylbenzene, however, the object for increasing activity stability can be achieved only when the reaction is carried out under hydrogen atmosphere.
The main obstacles encountered during use of the zeolite beta are that, on the one hand, the structure is easy to be injured during removal of the template agent and, on the other hand, its activity stability is poor due to ease of dealuminization in the reaction process.
U.S. Pat. No. 4,605,637 proposes a process for treating a zeolite of lower acidity, for example, B-containing ZSM-5, B-containing zeolite beta, high silicon ZSM-5 zeolite and the like with aluminum phosphate material such as microcrystal AlPO4-5 and the like in a liquid aqueous system to migrate Al atoms into the framework of the zeolite, to increase the acidity and the pyrolysis activity of the zeolite.
CN 1043450A proposes a process for modifying zeolite beta, the process comprises calcining Na zeolite beta, extracting aluminum from part of its framework with an acid, then potassium-exchanging the resultant zeolite so that the potassium content of the zeolite will be 0.5-2.5 wt %, drying and calcining, an immersing at room temperature in a near neutral buffer solution of phosphorus salt including, such as, potassium hydrogen phosphate-potassium dihydrogen phosphate, hypophosphorous acid-potassium hypophosphite, phosphorous acid-potassium phosphite, for 4-10 hrs, with or without washing as needed, so that the phosphorus content of the zeolite will be 0.01-0.5 wt %, then drying and calcining; by this method the modified zeolite beta is suited as a hydrocarbon processing catalyst for hydroisomerization reaction.
CN 1179994A proposes a process for modifying zeolite beta, the process comprises exchanging a Na-zeolite beta with ammonium ion to a Na2O content of the zeolite of less than 0.1 wt %; then treating said ammonium ion exchanged zeolite beta with an acid to extract aluminum atoms from part of its framework to increase the silica-alumina ratio to higher than 50; mixing homogeneously thus dealuminized zeolite beta with phosphoric acid or a phosphate, then oven-drying the resultant mixture to make the obtained zeolite having 2-5 wt % of P2O5 content; finally hydrothermal-calcining the obtained zeolite at 450-650° C. under a steam atmosphere for 0.5-4 hrs. When the zeolite beta modified by this process is used for cracking reaction of hydrocarbons, higher yield of olefins can be obtained, in particular higher yield of isomeric olefins and lower yield of coke.
CN 1205249A proposes a process for modifying zeolite beta, the process comprises mixing homogeneously the raw powder of a synthesized zeolite beta with a mixture containing Al2O3 source, P2O5 source, SiO2 source, H2O2 and water in a weight-ratio of zeolite beta:Al2O3:P2O5:SiO2:H2O2:H2O=1:(0.001-0.02):(0.01-0.30):(0-0.05):(0-0.10):(1.0-3.0), then drying and further rising the temperature to 400-650° C. and calcining the mixture thus obtained for 1-5 hrs, then exchanging the calcined zeolite with ammonium ion by using a conventional method to reduce the Na2O content of the zeolite to less than 0.1 wt %. This process can obviously improve the activity stability of the zeolite betas and the crystallization retention can be increased as well.